Carrying out catalytic oxidations in the gaseous or vapor state



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Patented Dec. 4,1928. I

- 1,693,915 UNITED STATES PATENTOFFICE.

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MING-OUT CATALYTIC OXIDATIONS IN THE GASEOUS OR VAPOR STATE,

Io Drawing. Application filed April 25, 1927, Serial No. 186,665, and in Germany June 14, 1926.

In the catalytic oxidation of organic substances in the gaseous or vapor statethe reaction products are'usually recovered 1n a SOlld or liquid condition by cooling the resulting 6 reaction mixtures. It frequently happens ac- 1 cordingto this method of working, and especially when impure initial materials are used, that the-separated reaction products are con-- taminated by-by-products, and it is often im- 1 possible tomake use of such contaminated roducts without previous purification.

us, for example, when using technical naphthalene pro nets in the catalytlc production' of phthalic anh dride according to the own, a (grey product of imper cct.puri.ty.is obtaine e Wehave now foundthat pure, or practically pure, products maybe obtained in the catalytic oxidation of organic compounds in 2 the vapor state, by bringing the reaction mix. ture, com'in from the reactionchamber, into contact wit solidsubstances, prior to the separation of the reaction products. The action of the solid substances is probably due to a kind of selective adsorption, but we do not wish to bind ourselves to this explanation of the result obtained. Generally speaking such solid substances as havea large super- -ficial area, for example, granulated pumice, silica e1, active carbon, and the like, are most suitable, but other mauterials which may have 'a surface only slightly rough or evensmo'oth, for example marble, .calamine (zinc carbonate)' or iron turnings or the like, give also good results.

any case the solid substances must be'so chomn, that they do not alter theirshape at that means that they do not melt or volatilize, and that the do 40 'notreact with the desired reactio'npro nets and arenot decomposed by the hot gases with be the formation of products which would re-.

act with or contaminate the desired reaction product. Thusfor example calamine ma employed even at ten) eratures at-whichI carbon diox'id is split 0 whereas-for example peat though it possesses a rather large superficial area, is unsuitable in most cases, as It would give ofi'.organic decomposition 30 products contaminating the dered reaction product at the temperature of workin In many instances the action-of the sub-' stances and the time for which they remain active, may bcjimproved by impregnating them, prior to use, with'solutions of salts or bases, or by coating them with salts or metallic oxids, 1 i

The temperature at which the solid substances are allowed to act must be maintained high enough as to avoid deposition of the desired reaction product. In most cases they will range about C. above the temperature at which the deslred'reaction product would separate out, but they may also be .much

tion ofthe reaction product itself b reason of a catalytic action of the solid su stances, which may lead for example to further oxidation or to the-splitting oflf of carbon dioxid. The most suitable temperatures vary with the nature of the solid can easily be ascertained. g

Inasmuch as a gradual diminution of-the purifying action of the said solid substances substances and Y occurs in prptracted use, it is advisable to apply them in the following'manner, namely to bring the reaction gases at-first into contact with partially spent solid substances and thereaftervinto' contact with such as are still efficient or fresh. A preferred method is to bring the said solid substances continuously into contact with the reaction mixture, on the counter-flow principle. This may be efl'ected,

for-example, by passing the reaction mixture up through a shaft filled with the said solid' substances and provided at the top and bottom with suitable devices, such as air-locks,

.removed at the bottom 7 freshor regenerated solid substances introduced at the top, without interrupting the continuit of the operation.

thereto..

oxidized in the known manner and ,the re- 'sulting gas mixture in which phthalic anhy dride 'is present with alpartialprmum of owing example further i1lus-- Y trate how our invention may be .carried out in practice, but .the invention is not Commercial naphthalene is catalytically" by means of which the spent substances can and replaced by.

' naphthoquinone are containe mixture having-um shape 'naphthoquinone,

about 3.5 millimetres mercury, is subjected to the above-described treatment prior to the .contains more than 99 per cent of phthalic anhydride. A special advantage of the process accordin to the present invention consists in the act that when sulfur-contaminated technical grades of na hthalene' are used, the sulfuric acid formed uring the oxidation is retained b the purifying mass, and phthalic anhydri e free from sulfuric acid is obtained direct j g If the oxidation-of the na hthalene be con-. ducted in such a way that ar e amounts of in the reaction mixture besides phthalic anhydride, the cooled separated product obtained after treating the saidmixture with the said solid substances, .for example, with granulated pumice, at about 200 0;, consists of a pure yellow mixture of phthalic anhydride and from which the pure naphthoquinone can easily be recovered, for instance by extracting the phthalic anhydride with weak alkalis, whereas in the absence of a treatment with solid substances, a large portion of the naphthoquinone undergoes conversion, and a valueless dark-colored product is deposited.

The said process ma also be emplo ed, as in the case of the oxi ation of napht alene, in connection with other catalytic oxidations in the gaseous state, such for example as the preparation of maleic anhydride and hemeuinone from benzene and its derivativesand' t e production of benzaldehyde and benzoic acid from toluene. It affords special advantages when sulfur-containing initial products, such as commercial-benzene, phenol or toluene, are used.

What we claim is:

1. In the catalytic oxidation of organic compounds, the ste of bringing the gaseous ergone the reaction, prior to the separation of the reaction roducts and at a temperature at which no eposition of the desired reaction product occurs, into contact with a solid substance not altering its at the temperature-of use and not giving rise to further conversion and contamination of the desired reaction product, and -capable of removing impurities from the reaction mixture.

2. In the catalytic oxidation of organic 'mixture solid substance not altering its s compounds, the ste of bringing the gaseous mixture having un ergone the reaction, prior to the separation of the reaction (products and at a temperature at which no eposition of the desired reaction roduct occurs, into contact with a solid su stance not altering its shape at the temperature of use, not giving rise to further conversionand contamination of the desired reaction product, and capable of removing impurities from the reaction mixture and having a large superficial area. 3. In the catalytic oxidatlon of organic compounds, the ste of bringing the gaseous mixture having un ergone the reaction prior to the separation of the reaction roducts and at a temperature at which no eposition of the desired reaction product occurs,into contact with a partially spent solid substance not altering its shape at the temperature of use and not giving rise to further conversion and contamination of the desired reaction product, and capable of removin the reaction mixture, and t substance of the said kind.

4. In the catalytic oxidation of organic compounds, the ste of bringing the gaseous having un ergone the reaction prior to the separation of the reaction products and at a temperature at which no deposition of on with a fresh impurities from the desired reaction product occurs, into contact on the counterflow principle, withha ape at t e temperature of use and not giving rise to fur- .ther conversion and contamination of the desired reaction products. a

a 5. In the catalyticoxidation of naphthalene, the step of bringing the gaseous mixture having undergone t separation of the reaction products and bee reaction, prior to the tween about'150 and 250 0., into contact with a solid substance not altering its shape at the temperature of use and not 'ving rlse to further conversion and contamination oi the desired reaction product, and capable o :emoving impurities from the reaction mixure.

6. In the catalytic oxidation of naphthalene, the step of bringing the gaseous mixture having undergone the reaction, separation of the reaction products and at about 200 0., into contact with granulated pumice. 1

In testimony whereof we our hands.

Jonams .BRoDE. ADOLF JOHANNSEN.

have hereunto set prior to v the CERTIFICATE or CORRECTION.

man No. 1,693,915. Granted December 4; 1928. to

' JOHANNES BRODE ET AL,

vlt is hereby certified that error appears in the-printed specification of the above numbered patent requiring correction is follows: I Page 2,- line 92, aftertheivord "products" and before the period insert the comma and words and capable of removing impurities irom'the" reaction mixture"; and that the said" Letters Patent should be read with this correction therein that the same may conform to the record of the case. in the Patent Office.

Signed and sealed this 15th day of January, A; D.- 1929.

M11. Moore;

(Seal) I I p Acting Conmi'eeioner oil'atente. 

